#define _CRT_SECURE_NO_WARNINGS 1

//https://leetcode.cn/problems/max-area-of-island/

class Solution {
    typedef pair<int, int> PII;
    int dx[4] = { 0,0,1,-1 };
    int dy[4] = { 1,-1,0,0 };
    vector<vector<bool>> vis;
    int m, n;
public:
    int bfs(vector<vector<int>>& grid, int i, int j)
    {
        queue<PII> q;
        q.push({ i,j });
        vis[i][j] = true;
        int ret = 1;
        while (q.size())
        {
            auto [a, b] = q.front();
            q.pop();
            for (int z = 0; z < 4; z++)
            {
                int x = a + dx[z], y = b + dy[z];
                if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == 1 && vis[x][y] == false)
                {
                    q.push({ x,y });
                    vis[x][y] = true;
                    ret++;
                }
            }
        }
        return ret;
    }
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        m = grid.size(), n = grid[0].size();
        vis.resize(m, vector<bool>(n));
        int ret = 0;
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                if (grid[i][j] == 1 && vis[i][j] == false)
                {
                    ret = max(ret, bfs(grid, i, j));
                }
            }
        }
        return ret;
    }
};